The influence of carbon morphologies and concentrations on the rheology and electrical performance of screen-printed carbon pastes

Screen-printing inks containing various morphologies of carbon are used in the production of a variety of printed electronics applications. Particle morphology influences the rheology of the ink which will affect the deposition and therefore the electrical performance of a printed component. To assess the effect of both carbon morphology and concentration on print topography and conductivity, screen printable carbon inks with differing loading concentrations of graphite, carbon black and graphite nanoplatelets (GNPs) were formulated, printed and characterised, with rheological and novel print visualisation techniques used to elucidate the mechanisms responsible. Carbon morphology had significant effects on the packing of particles. The smaller carbon black particles had more interparticle interactions leading to better conductivities, but also higher ink viscosities and elasticities than the other morphologies. Increases in carbon concentration led to increases in film thickness and roughness for all morphologies. However, beyond a critical point further increases in carbon concentration led to agglomerations of particles, mesh marking and increases in surface roughness, preventing further improvements in the print conductivity. The optimal loading concentrations were identifiable using a custom-made screen-printing apparatus used with high speed imaging for all morphologies. Notable increases in filamentation during ink separation were found to occur with further increases in carbon concentration beyond the optimum. As this point could not be identified using shear rheology alone, this method combined with shear rheology could be used to optimise the carbon concentration of screen-printing inks, preventing the use of excess material which has no benefit on print quality and conductivity.

Optimization of flexo process parameters to reduce the overall manufacturing cost

The flexo process parameters play an important role in ink transfer and will lead to wastage of inks, substrate, solvents and printed stocks if not monitored and controlled. The work focuses on optimizing the flexo process parameters for 40 microns 3-layer polyethylene (PE) film with Blue Nitrocellulose (NC) ink to reduce overall manufacturing cost while maintaining the print quality for diaper application. An experimental design was conducted for the response Ink GSM (grams per square meter), ?E and Print Mottle with factors such as ink viscosity, anilox volume, plate dot shape and substrate opacity. The data was analyzed through Main Effect, Interaction Plot and Analysis of Variance (ANOVA). The regression models were developed for the response to validate the predictive ability of model. The process optimization resulted in reduction of Ink GSM, ?E and Print Mottle by 18%, 52% and 1% respectively. The ink consumption reduced by 18.26% with minimized print defects, thereby reducing the overall manufacturing cost.

Simulation study of droplet formation in inkjet printing using ANSYS FLUENT

Flow simulations of jetting of inkjet drops are presented for water and ethylene glycol. In the inkjet printing process, droplet jetting behaviour is the deciding parameter for print quality. The multiphase volume of fluid (VOF) method is used because the interaction between two phases (air and liquid) is involved in the drop formation process. The commercial inkjet printer has a nozzle diameter of ∼73.2μm. In this work, a simulation model of inkjet printer nozzles with different diameters 40μm, 60μm, and 80μm are developed using ANSYS FLUENT software. It is observed that when water is taken as solvent then the stable droplets are generated at 60μm nozzle diameter till 9μs because of its low viscosity. For higher diameter, the stamen formation is observed. Ethylene glycol stable droplets are achieved at 80μm nozzle diameter till 9μs because of their high viscosity (∼10 times that of water). Along with the droplet formation, the sustainability of the droplet in the air before reaching the substrate is also important. The simulation model is an inexpensive, fast, and flexible alternative to study the ink characteristics of the real-world system without wasting resources.

Traditional Artificial Neural Networks Versus Deep Learning in Optimization of Material Aspects of 3D Printing

3D printing of assistive devices requires optimization of material selection, raw materials formulas, and complex printing processes that have to balance a high number of variable but highly correlated variables. The performance of patient-specific 3D printed solutions is still limited by both the increasing number of available materials with different properties (including multi-material printing) and the large number of process features that need to be optimized. The main purpose of this study is to compare the optimization of 3D printing properties toward the maximum tensile force of an exoskeleton sample based on two different approaches: traditional artificial neural networks (ANNs) and a deep learning (DL) approach based on convolutional neural networks (CNNs). Compared with the results from the traditional ANN approach, optimization based on DL decreased the speed of the calculations by up to 1.5 times with the same print quality, improved the quality, decreased the MSE, and a set of printing parameters not previously determined by trial and error was also identified. The above-mentioned results show that DL is an effective tool with significant potential for wide application in the planning and optimization of material properties in the 3D printing process. Further research is needed to apply low-cost but more computationally efficient solutions to multi-tasking and multi-material additive manufacturing.

Determining the Print Quality Due to Deformation of the Halftone Dots in Flexography

This paper researches the issues related to the print quality in flexography, especially the influence of the print run and inadequate printing settings on dot deformation. Dot deformation can lead to inconsistencies in print quality, such as a loss of highlight tones or an unpredictable increase in tonal value. This research was conducted on two concrete examples of flexible packaging printed on transparent films. All significant parameters of dot deformation were evaluated, including dot coverage, dot sharpness and the uniformity of the ink density. The increase in the coverage values in the midtones was linear throughout the entire print run, while in the light tones, it was more logarithmic. The overall percentage deviations from the reference value were 6.3% in the midtones and 52.6% in the light area. The increase in dot coverage was due to the wear of the polymer plate, which caused the side shoulders of the dot to become a part of the printing surface. An analysis of the ink density showed a much more homogeneous shape of the dot at the beginning of the print run. The correct ratio of the anilox roller line screen to the line ruling of the printing plate is important in order to ensure a minimum dot size in print.

Optimization of Printing Parameters for Digital Light Processing 3D Printing of Hollow Microneedle Arrays

3D printing is an emerging technology aiming towards personalized drug delivery, among many other applications. Microneedles (MN) are a viable method for transdermal drug delivery that is becoming more popular for delivery through the skin. However, there is a need for a faster fabrication process with potential for easily exploring different geometries of MNs. In the current study, a digital light processing (DLP) method of 3D printing for fabrication of hollow MN arrays using commercial UV curable resin was proposed. Print quality was optimised by assessing the effect of print angle on needle geometries. Mechanical testing of MN arrays was conducted using a texture analyser. Angled prints were found to produce prints with geometries closer to the CAD designs. Curing times were found to affect the mechanical strength of MNs, with arrays not breaking when subjected to 300 N of force but were bent. Overall, DLP process produced hollow MNs with good mechanical strength and depicts a viable, quick, and efficient method for the fabrication of hollow MN arrays.

Sorting Device Coding Print Quality Machine on Packing Box Prototype Utilizing Optical Character Recognition

The design of a system that can recognize the characters printed by the coding machine so that it can then determine the assessment of very good and bad prints, is the goal of this research. This system is useful as an indicator of an indication of a problem with the coding machine which is indicated by the number of products rejected by the system. In addition, this system is an effort to reduce printing errors so that they are sorted and do not pass to the market, thus causing misinformation to the public. This system is in the form of a moving conveyor table that has a firing area box and a reject rod as a product separator. The OCR method is programmed in a computer that is part of the system, to be able to recognize the characters printed by this coding machine. USB to TTL which functions as serial communication from the Laptop to the Microcontroller, is a complement to this tool. Testing as many as 60 times on 12 types of characters, this system has been carried out on this tool. There are six types of good characters and six types of bad characters, which have been provided. Of the 60 tests, the results were four failed tests. That is, the percentage of success of this tool is 93.33%, and the percentage of error is 6.66%.

Development of rapid set mortar for additive manufacturing

The study presents the development results of blended cement mortars for additive manufacturing. The goal was to achieve a balanced rheological behaviour of the fresh mixture through optimal granulometry, suitable grain shape and the choice of micro-admixtures. The article closely describes the granulometric and rheological characterization of the proposed ternary and quaternary blended mortar mixtures with various SCM’s. The print quality and shape stability of the promising mortars and the researched 3DP mixes were evaluated during incremental layering for comparison. The performed experiments confirmed that the mixtures containing blast furnace slag, quartz powder and metakaolin are more plastic and allow faster layering in height. The slaked lime-enriched mixture has excellent plasticity and is able to resist deformation during overlaying, the printed layers are without surface defects. The small addition of polypropylene fibre (0.08 wt.%) improves the plasticity and shape retention ability.

Comparison of Properties of 3D-Printed Mortar in Air vs. Underwater

Research and technological advancements in 3D concrete printing (3DCP) have led to the idea of applying it to offshore construction. The effect of gravity is reduced underwater, which can have a positive effect on 3DCP. For basic verification of this idea, this study printed and additively manufactured specimens with the same mortar mixture in air and underwater and evaluated properties in the fresh state and the hardened state. The mechanical properties were evaluated using the specimens produced by direct casting to the mold and specimens produced by extracting from the additive part through coring and cutting. The results of the experiment show that underwater 3D printing required a greater amount of printing output than in-air 3D printing for a good print quality, and buildability was improved underwater compared to that in air. In the case of the specimen layered underwater, the density and compressive strength decreased compared to the specimen layered in air. Because there are almost no effects of moisture evaporation and bleeding in water, the interlayer bond strength of the specimen printed underwater was somewhat larger than that printed in air, while there was no effect of the deposition time interval underwater.

Correlation between Ink Thickness and "Shrink Sleeve" Flexographic Print Quality at a Stable Friction Coefficient

Flexographic technology usage is increasing in recent years. Predicted growth in the technology usage intensifies the demand for improved quality. It is expected that flexographic printing will achieve greater results than ever before. Since this technique is used in the printing of shrink sleeve packaging, it is imperative to meet the technical and economic requirements of the shrink sleeve product. This is primarily to ensure gliding of the white printing material. The amount of white should be as small as possible, making the sliding of the material optimal and the quality of the print better. Therefore, the quality of the printing was measured by changing the conditions of slippage and white color. This research has established a correlation between the thickness of the white layer and the reduction of print quality over thin lines.